RU2502950C1 - Method for topographic imaging of streamlining of moving object - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method is realised using a double-beam interferometer with an optical system for generating a reference beam and an object beam, a system of mirrors mounted along reference and object branches, a working area, a projection lens and a hologram recording unit. A hologram is recorded using a double-exposure technique. The analysed moving body is not in the working area during the first exposure. The working area is formed by first and second plane-parallel mirror plates which form equal but oppositely signed angles with the optical axis. During second exposure, a body moving with supersonic speed is directed into the working area through an opening in the second plane-parallel mirror plate, wherein gas-dynamic flow near said body is analysed. Simultaneously, an object beam, the vector $$\overrightarrow{E}$$

of which is parallel to the vector $$\overleftarrow{V}$$

of the speed of the analysed moving body but opposite in direction, is propagated in the working area.

EFFECT: broader technological capabilities of the method for holographic imaging of the streamlining of moving bodies by obtaining density distribution in a radial direction through frontal illumination of gas-dynamic flow.

1 dwg

Description

The invention relates to the field of optical instrumentation and can be used in combustion physics when studying the processes of mixing, ignition and combustion of fuels, visualizing flame flames flowing out of nozzles, in experimental gas dynamics, in ballistic installations when studying the flow around bodies at supersonic speeds, and also in other similar areas.

A known method of holographic visualization of the flow around moving bodies in ballistic installations (see V.T. Chernykh. "Holographic interferometry of phase objects" - L.: "Science", Leningrad. Department, 1979 / A.F. Belozerov and etc., pp. 168-170 and 212-216) by sequentially recording on the recording medium an object wave that has passed through the gas-dynamic flow and a reference wave.

There is also a method of holographic visualization of the flow around moving bodies (see R. Collier, K. Berkharm, L. Lin, “Optical holography” - M .: Mir, 1973, p. 479), in which the sequential registration of object and reference waves on the recording medium is carried out by two-exposure method.

The closest technical solution is the method of holographic visualization of the flow around a moving body in an aeroballistic installation (see V.T. Chernykh "Investigation of the motion of bodies in two-phase flows by the holographic method. / Dukhovskiy I.A., Kovalev P.A. et al.," Optics and spectroscopy ”, v.63, v.5, p.1005-1008, 1987) by means of a two-beam interferometer containing optically coupled laser, a beam splitter for the formation of the reference and object branches, collimators of the reference and object branches, a system of mirrors mounted along op molecular weight and object branch, the work area, a projection lens and a hologram recording assembly, by successively recording on the recording medium the reference wavefront and the object wavefront that has passed through the gas-dynamic flow around a moving body, perpendicular to the flow velocity vector.

A disadvantage of the known methods is the limited technological capabilities for holographic visualization of the flow around a moving body, due to the fact that by means of these methods the gas-dynamic flow under study is detected only along the normal to the flow velocity vector, both in the meridional and in the sagittal planes. The obtained holographic interferograms are used to calculate the distribution of the density field in the indicated planes in different sections of the flow, both in the head shock wave and in the wake of the moving body.

However, it is of practical interest to study the flow around a body moving at supersonic speed in the case when the object wavefront is directed along the path of the body and the wavefront shines through the flow towards the velocity vector of the moving body.

The objective of the invention is to expand the technological capabilities of the method of holographic visualization of the flow around moving bodies.

которого параллелен вектору $$\overleftarrow{V}$$

скорости исследуемого движущегося тела, но противоположен по направлению.The technical result is achieved by the fact that in the method of holographic visualization of the flow around a moving body by means of a two-beam interferometer with an optical system for forming the reference and object beams, a system of mirrors installed along the reference and object branches, a working area, a projection lens and a hologram recording unit, by sequential recording on the recording medium of the hologram registration unit of the reference beam and the object beam, while the object beam shines through the working area moving the body is focused using a projection lens into the plane of the recording medium, and the hologram is recorded by the two-exposure method, and during the first exposure the moving body under study is absent in the working area, according to the invention, the working area is formed using the first and second plane-parallel mirror plates forming with an optical axis equal angles, but opposite in sign, and during the second exposure to the working area through the hole made in the second plane-parallel mirror plate, on the body moving at a supersonic speed is controlled by the gas-dynamic flow near which it is investigated, and at this time an object beam propagates in the working zone, the vector $$\overrightarrow{E}$$

which is parallel to the vector $$\overleftarrow{V}$$

the speed of the investigated moving body, but opposite in direction.

The invention is illustrated by the drawing, which shows a two-beam interferometer for implementing the proposed method of holographic visualization of the flow around a moving body.

The numbers in the drawing indicate:

1 - laser

2 - a beam splitter,

3 - collimator of the object branch,

4 - the first plane-parallel plate (first mirror of the object branch),

5 - the second plane-parallel plate (second mirror of the object branch),

6 - projection lens

7 - node hologram registration,

8 - the first mirror of the supporting branch,

9 - the second mirror of the supporting branch,

10 - collimator of the supporting branch,

11 - working area

12 - hole made in the second plane-parallel plate,

13 - the investigated body moving with supersonic speed.

A double-beam interferometer contains an optical system for forming the reference and object beams, a system of mirrors mounted along the reference and object branches. The double-beam interferometer contains an optically coupled laser 1, a beam splitter 2 for forming the reference and object branches, an object branch collimator 3, a working zone 11, an object branch mirror system, a projection lens 6 and a hologram registration unit 7, a reference branch mirror system consisting of the first 8 and second 9 mirrors, collimator 10 of the supporting branch.

In a two-beam interferometer, the system of mirrors of the object branch is made in the form of the first 4 and second 5 plane-parallel plates, forming equal angles with an optical axis, but opposite in sign.

In the second plane-parallel plate 5, a hole 12 is made, the diameter of which is larger than the diameter of the investigated body 13 moving with supersonic speed.

The mirror system of the object branch is installed in the working area 11, between the collimator 3 of the object branch and the projection lens 6.

According to the proposed method of holographic visualization of the flow around a moving body 13, using the described two-beam interferometer, in the plane of the recording medium of the hologram recording unit 7, the reference W _op and the object W _about light beams are sequentially recorded. Object beam W _of translucent working zone 11. By means of the projection lens 6 is focused moving body 13 in the plane of the recording unit 7, the hologram recording medium. The hologram is recorded by the two-exposure method, and during the first exposure, the investigated moving body 13 is absent in the working zone 11. The working area 11 is formed using the first 4 and second 5 plane-parallel plate-mirrors, forming equal angles with an optical axis, but opposite in sign.

которого параллелен вектору $$\overleftarrow{V}$$

скорости исследуемого движущегося тела, но противоположен по направлению.During the second exposure, a body 13, moving at a supersonic speed, the gas-dynamic flow around which is being studied, is directed through the hole 12, made in the second plane-parallel mirror plate 5, into the working zone 11. At this time, in the working area 11 spread the object beam W _about , vector $$\overrightarrow{E}$$

which is parallel to the vector $$\overleftarrow{V}$$

the speed of the investigated moving body, but opposite in direction.

An example of a specific implementation.

Coherent radiation from the laser 1 by means of a beam splitter 2 is divided into reference W _op and object W _about light beams. These beams arrive, respectively, in the collimators 3 and 10 of the object and reference branches. Next, the object beam W _{about is} reflected from the first plane-parallel plate (mirror) 4, illuminates the working area 11 and, reflected from the second plane-parallel plate (mirror) 5, enters the projection lens 6. The projection lens 6 matches the plane of the working zone 11 with the plane of the recording medium of the node 7 hologram registration.

The reference beam W _op using mirrors 8 and 9 is introduced into the collimator 10 of the reference branch. The reference beam W _op enters the plane of the recording medium of the hologram recording unit 7 at an angle θ to the object beam W _rev .

The hologram is recorded by a two-exposure method.

During the first exposure, the object of study (the investigated moving body 13) is absent in the working area 11.

During the second exposure, a body 13 enters the working zone 11 through the hole 12 made in the second plane-parallel plate (mirror) 5, moving at a supersonic speed, the gas-dynamic flow near which is being studied.

которого параллелен вектору $$\overleftarrow{V}$$

скорости исследуемого тела 13, но противоположен по направлению.As shown in the drawing, at this time in the working area 11 is distributed object beam W _about , vector $$\overrightarrow{E}$$

which is parallel to the vector $$\overleftarrow{V}$$

the speed of the investigated body 13, but opposite in direction.

When reconstructing wave fronts from a hologram, an interference image is obtained, the stripes of which are concentric in shape and correspond to the observation plane perpendicular to the optical axis of the object branch. These bands correspond to lines of equal density and will characterize the radial distribution of density around a moving body.

The authors proposed such a solution for the first time in the practice of gas-dynamic research.

It should be noted that when studying the flow around bodies (for example, a sphere model) that create axisymmetric flows, the scatter along the motion path is quite small, and the diameter of the hole in the plate (mirror) 5 can exceed the diameter of the body by several millimeters. When solving other ballistic problems, the diameter of the hole in the plate (mirror) 5 should be selected taking into account the spread of the trajectory of the body.

Thus, a new method was created that made it possible to expand technological capabilities in holographic visualization of the flow around a moving body.

Using the proposed method will allow to obtain holographic interferograms corresponding to the frontal transillumination of the gas-dynamic flow, and thereby obtain quantitative information about the density distribution in the radial direction.

Claims (1)

A method for holographic visualization of a flow around a moving body by means of a two-beam interferometer with an optical system for forming the reference and object beams, a system of mirrors mounted along the reference and object branches, a working area, a projection lens, and a hologram recording unit, by sequentially recording the reference beam hologram registration unit on the recording medium and the object beam, while the object beam shines through the working area, the moving body is focused using the projection volume a hologram into the plane of the recording medium, and the hologram is recorded by the two-exposure method, and during the first exposure, the moving body under study is absent in the working area, characterized in that the working area is formed using the first and second plane-parallel mirror plates, forming equal angles with the optical axis but opposite in sign, and during the second exposure, a body moving at a supersonic speed is guided through a hole made in the second plane-parallel plate-mirror for about amicheskoe is investigated, and at that time in the work area object beam spread vector $$\overrightarrow{E}$$

which is parallel to the vector $$\overleftarrow{V}$$

the speed of the investigated moving body, but opposite in direction.

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